Parasites of the CNS Flashcards
You are presented with a horse that is:
- Stumbling and falling over the past week
- Is unsteady in its hindlimbs
- Has slight wear on the dorsum of its toes on the hindlimbs, so dragging its feet
- has left-sided gluteal muscle atrophy
- was able to be pulled to the left on the tail-pull test
- No cranial nerve deficits
Most common Presentation are the 3A’s: Asymmetric, Ataxic and focal muscle Atrophy
You suspect a parasitic infection, what is the possible etiology?
Sarcocystis neurona = equine protozoal myeloencephalitis (EPM)
This is an apicomplexa parasite
How can you confirm the presence of Sarcocystis neurona?
1) Immunoblot analysis
- S. neurona antibodies in serum and CSF
CSF: Sn and Sp of 89%
Serum: Sn of 89% and Sp of 71%
2) ELISA: Highly specific for S.neurona specific antibodies
note: You cannot do a PCR, its sensitivity is very low as Merozoites are not found in the CSF, and any free parasite DNA floating around is rapidly destroyed
3) PM: Acute hemorrhagic lesions and necrosis in the spinal cord
What is the Final Host to S. neurona ?
Opossum
What are the Intermediate hosts to S. neurona ?
- Domestic Cat
- Several wildlife species including raccoons, skunks, armadillo
What is the Aberrant (“dead-end”) host to S. neurona ?
- Horse
Where does Schizogony occur in the horse?
Muscle tissue, producing merozoites
Merozoites penetrate and infect neural tissue
What is treatment for S. neurona in horses?
- Ideal drug: Ponazuril: Antiprotozoal Oral Paste, 5mg/kg/day ~28 days
- Sulfonamides: Sulfadiazine orally, 20mg/kg
- Diclazuril and Toltrazuril: coccidiostat that kills parasites in early stages, used as a prophylactic
- NSAIDs
- Vitamin E
Caution: steroids are contraindicated in this case
How can S. neurona infection be prevented?
- Prevention is best
- Keep feed rooms and containers closed and sealed
- Prevent wildlife from getting into feed room
- Discard dropped grain to discourage birds/ scavengers
What is the Definitive/ Final Host of Neospora. caninum ?
- Dogs (incl dingo, coyotes and wolves)
NOT foxes! Cant blame them
What is the Intermediate host of Neospora caninum ?
- Mammals and birds
- Cattle being the main issue
Why is Neospora caninum important in cattle?
- Highly prevalent
- Causes 10-45% of abortions
How do dogs or other wild canids get Neospora caninum ?
- Eating tissue cyst infected meat/ placental tissue = exogenous transmission
- transmission via placenta or milk to puppies (usually the litter is all affected)
How do cattle get Neospora. caninum ?
- Eating infected food (silage or pasture) with oocysts = exogenous transmission
- Vertical transmission from cow to calf = endogenous transmission
Is Neospora. caninum transmissible to humans? (i.e. zoonotic)
No
How does Neospora. caninum affect the cow fetus?
- Multiplying tachyzoites cause cell necrosis in the fetal macrophages, neutrophils, spinal fluid, and other neural cells
How does Neospora. caninum affect the adult/ mature cow?
- Little or no pathology, unless immunocompromised
What will happen to a cow fetus if infected with Neospora. caninum early in gestation?
- Abortion
What will happen to a cow fetus if infected with Neospora. caninum mid to late gestation?
- Variety of congenital defects including neurological signs, myocarditis, ataxia, exopthalmia
- Can be born normal and be a persistent shedder
- Can be born normal and uninfected
Clinical signs will vary according to:
- Quantity and duration of parasitemia
- Effectiveness of maternal immune response
- Ability of fetus to mount an immune response
What usually has to happen in order for a dog to present with clinical signs of Neospora caninum?
Immunosuppression
Therefore presentation is as follow:
- Presents in puppies due to weak immune system
- Presents in dogs concurrently infected with Canine distemper or Ehrlichiosis
- Presents in older dogs with waning immune systems or treatment with steroids
What are the clinical signs associated with Neospora caninum in a YOUNG dog?
- Encephalomyelitis: hyperexcitability, depression, paresis/ paralysis, head tilt, seizures
- Myositis-polyradiculoneuritis: progressive pelvic limb paresis (bilateral, non-painful, rigid pelvic limbs)
How can Neospora caninum be diagnosed in a young dog showing neurological clinical signs?
- Clinical signs are a big indicator, especially if multiple littermates are showing signs
- IgG titer in serum
- Presence of antibodies in CSF
- Positive response to appropriate treatment
What is the treatment for Neospora. caninum in dogs?
- No perfect drug or combination available
Can try:
- Trimethoprim sulfadiazine + Pyrimethamine
- Trimethoprim sulfadiazine + Clindamycin
- Clindamycin
What is the treatment for Neospora. caninum in cattle?
- No effective treatment
- Culling of seropositive stock in the breeding herd
What is the Intermediate host of Toxoplasma. gondii?
- Sheep
- Humans
- (Warm-blooded animals)
- NOT common in cattle or horses
What can Toxoplasmosis cause in sheep and humans?
Abortion is the greatest occurrence
How can Toxoplasma be diagnosed in cats?
- Fecal sample, Detection of oocysts in the feces
- Serology: IgM:IgG ratio but not specific
- PM: immunohistochemical staining of the brain tissue
note: hematology is non-specific. No single test will give a definitive diagnosis. PCR is not useful
How can Toxoplasma be diagnosed in sheep?
- Biopsy
- Post Mortem
- Immunohistochemistry
- PCR
- Serology
How can Toxolpasma be diagnosed in Humans?
IgM/ IgG ratio and affinity
What is the treatment protocol for Toxoplasmosis in sheep?
No satisfactory drug treatment
Is there a vaccine for Toxoplasma?
Yes, available for sheep, but can be used on goats (extra-labelled)
- Toxovax (attenuated live vaccine)
- Toxovax provides good immunity to sheep, give before pregnancy and she is not likely to abort
How can Toxoplasma be prevented best in sheep?
- Prevent access of cats to feed and bedding
How can Toxoplasma be prevented best in pregnant or immunocompromised humans?
- Avoid contact with cat feces
- Avoid contact with soil (outdoor cats defecate in)
- Avoid eating raw or undercooked meat
How can Toxoplasma be prevented best in cats?
- Feed only dried or canned or cooked food
- Keep indoors
- Frequent cleaning of cat litter
What usually has to happen for a cat to show clinical signs when infected with Toxoplasma gondii?
What clinical signs would you look out for?
Immunosuppression
- Usually concurrently infected with FIV
Clinical signs: behavioral changes, seizures, ataxia, muscle hyperesthesia, paresis/ paralysis, blindness
What is the treatment of Toxoplasmosis in Cats?
- Azithromycin
- Clindamycin
- Trimethoprim-sulfa
What is the final host of T. multiceps?
Dogs and wild canids (fox, jackal)
What is the intermediate host of T. multiceps?
- Sheep mainly
- Goats
- Deer
- Cattle
- Pigs
- Horses
- Human (Quite rare)
Dogs and wild canids are largely unaffected by the adult T. multiceps tapeworm, however what clinical signs do sheep and other intermediate hosts encounter when infected with the metacestode stage?
- Meningoencephalitis
‘Gid’ or ‘Staggers’ = Head pressing, head tilt, blindness, circling and high stepping gate
Dullness, anorexia, weight loss
How can T. multiceps be treated and controlled in sheep, goats and other intermediate hosts?
- Localize and decompress the cyst in the brain
- Treat dogs for tapeworms, and don’t feed dogs undercooked sheep carcass or viscera
What clinical signs are associated with Babesia infection in dogs?
- Fever
- Pale mucous membranes
- Icterus
- Haemogloburia
- Depression
- Haemoglobinemia
- Weakness
- Paddling, ataxia and coma due to the distension of capillaries in the cerebrum/ cerebellum leading to edema
How can Babesia be diagnosed in dogs?
- Blood smear stained with Giemsa stain
- ELISA or IFAT
- PCR
- PM lesions: splenomegaly
How is Babesia transmitted to dogs?
Brown dog tick and Ornate Cow Tick
Both not found in Ireland, BUT are found in other areas of Europe and America
